Portable electronic devices are becoming more and more prevalent in every aspect of society. The phenomenal increase in the use of these devices has simultaneously increased demand for batteries to power them. The batteries are usually contained within the device or in a separate battery pack. The batteries come in numerous shapes and sizes and may use any of a number of underlying technologies—e.g., lithium ion, nickel metal hydride, and so forth.
One disadvantage of portable electronic devices is that the battery is susceptible to failure, particularly when physically damaged or breached. Physical damage may cause a fire, explosion, or hazardous leak. The risk of failure from physical damage is higher in situations where the battery and device are exposed to extreme conditions such as in the military, construction, and the like.
In the military, soldiers often need to communicate and share information with other troop members and leaders. Soldiers are provided with portable electronic devices that allow effective communication, enhanced situational awareness, and improved fighting capabilities. For example, soldiers may be given electronic GPS units, night vision goggles, two-way radios, illuminated scopes, and so forth.
These devices require an ever increasing number of batteries to keep the soldier operational for extended periods of time. The soldier may be required to carry multiple batteries depending on the number of electronic devices present. The batteries are often placed in close proximity to the soldier's body to maximize mobility and stability.
Rechargeable lithium ion batteries are widely used due to their high energy density and low weight. The drawback of these batteries in a military context is that they can explode or burst into flames when they are pierced or impacted by a bullet or shrapnel. This may cause further injury to the soldier who may already be in a very dangerous situation.
The danger associated with lithium ion batteries has hindered their widespread use in the military. To increase the adaptation of lithium ion power sources by the military, many of the known problems must be addressed by modification of the cell chemistry and/or packaging of military battery packs.
Researchers have extensively investigated the lithium ion chemistry with the goal of creating abuse tolerant lithium ion cells. Many of these studies have focused on investigating the thermal and electrochemical contributions to lithium ion battery fires. It is widely believed that the survival of a lithium ion cell is dependent upon the relative rate of heat removal and heat generation. In the case where heat generation is greater than heat removal, “thermal runaway” will occur. It has been determined that thermal runaway for lithium cobalt oxide, a component found in many lithium ion batteries, began at approximately 180° C. for a fully charged cell.